The invention generally relates to the field of the design configuration of a circuit breaker which is used in low-voltage power supply systems. Preferably, it relates to a circuit breaker which can be used for an embodiment of the bearing for the switching shaft in a switch.
Low-voltage circuit breakers include two or more assemblies which are matched to the various task elements and are connected to one another during the production of the circuit breakers. The largest assembly is in this case the switching pole assembly, that is to say the switching poles which are arranged in a common housing or in individual housings which are connected to form a unit. The expression switching pole is intended to refer to all parts of a circuit breaker which are associated with the same pole of a circuit, in particular the contact system which includes stationary and moving contacts, with its supporting elements, its insulating elements and its coupling linkages for coupling the contact system of the switching pole to a switching shaft which is shared by all the switching poles. The movement sequences which are produced by a drive apparatus are transmitted to the switching shaft by way of a further coupling linkage which is associated with the drive.
Until now, the switching shaft has been physically associated either with the drive apparatus or with the switching pole assembly. In one known circuit breaker, in which the switching shaft is physically associated with the drive apparatus, the switching shaft is arranged in its central regionxe2x80x94in which the drive force is introduced into the switching shaftxe2x80x94in parallel walls, which are connected to one another and which form the supporting mechanism for the drive apparatus. The two ends of the switching shaft are mounted in further walls, which are connected to the walls which support the drive apparatus (DE 44 16 090 C1). A functional test of the switching pole assemblyxe2x80x94in particular a test to determine whether the movement which is provided by the drive apparatus will achieve correct closure of the contact arrangements of the switching poles with the required contact forcexe2x80x94cannot be carried out until the switch has been assembled completely.
In another known switch, in which the switching shaft is physically associated with the switching assembly, the switching shaft is formed in two parts and is held in its central region by a main bearing body. In this case, the main bearing body is in each case fitted with one end of the two switching shaft parts, and is at the same time used to fix these two switching shaft parts axially at one end. The other axially outer end of the two switching shaft parts is in each case held by in each case one auxiliary bearing body, which is likewise connected to the switching pole assembly. The switching shaft is thus positioned geometrically on the switching pole assembly such that the switching pole assembly can be tested autonomously by a test apparatus which simulates the drive movement of the drive. On the other hand, this arrangement makes it possible to test the drive apparatus autonomously, as well, in order to determine whether it produces the necessary rotary movement of the switching shaft (DE 197 39 702 C1).
Against the background of this arrangement, in another known switch, the switching shaft is likewise physically associated with the switching pole assembly. However, the switching shaft is integral in this switch. In order to mount this integral switching shaft such that it is not sensitive to tolerances and is simple to install at the point at which the switching forces act, the two ends of the switching shaft have associated bearing bodies whichxe2x80x94surrounding the switching shaft in the form of half shellsxe2x80x94are mounted on the switching pole assembly (DE 199 48 716 C1). The bearing for the switching shaft is determined statically by way of a configuration such as this of the two axially outer bearing bodies. Depending on the length of the switching shaft, auxiliary bearing bodies to provide additional bearing for the switching shaft can be arranged in a known manner in this arrangement.xe2x80x94In this switch as well, both the switching pole assembly and the drive apparatus can be tested autonomously before being assembled.
However, the process of assembling these two assemblies can lead to the switching shaft no longer being rotated in the desired manner by the drive apparatus, owing to component tolerances, installation tolerances and switching shaft deformation in the central region of the switching shaft (in particular bending and torsion of the switching shaft in this region). For example, the rotation angle of the switching shaft may change, which leads to a change in the contact force between the stationary and the moving contacts. If the contact force is too great, the drive apparatus must be designed to be stronger, which necessarily results in more complex measures for shock damping. An excessively low contact force on the other hand leads to heating and to faster contact wear.
An embodiment of the invention is based on an object of refining the bearing assembly such that the installation position of the switching shaft after assembly of the drive apparatus and of the switching pole assembly corresponds to that position of the switching shaft on which the separate test of the drive apparatus was based.
According to an embedment of the invention, an object may be achieved in that, if the supporting mechanism of the drive apparatus is mounted on the switching pole assembly, the axially central bearing assembly has two bearing half shells, one of which is supported radially on the switching pole assembly and the other of which is supported radially on the supporting mechanism, and is fixed axially via guide surfaces.
With a refinement such as this, in which the bearing for the switching shaft is still determined statically, there is a precise geometric association between the drive apparatus and the switching pole assembly in the region where the drive forces are introduced. In this case, the bearing half shell which is associated with the switching pole assembly can advantageously be held in a captive manner between the switching pole assembly and the switching shaft.
The drive apparatus is normally coupled to the switching shaft by way of a bolt, which on the one hand passes through a first lever, which forms the end of a coupling linkage of the drive apparatus, and on the other hand passes through a second lever which projects radially from the switching shaft. If this bolt is provided with a bolt head and if the bearing assembly is arranged at a distance alongside one of the two levers, and one of the two bearing half shells is provided with a lug-like flange on the side associated with this lever, then the bolt can be fixed axially in a simple and reliable manner, by the lever and the lug-like flange forming side guide surfaces for the bolt head. In this case, the fitting of the bolt can be simplified in that the bearing half shell which is provided with the lug-like flange can be moved in the circumferential direction of the switching shaft in order to expose the bolt head when the supporting mechanism has been released from the switching pole assembly, and can be forced to move back to its mounting position by the other bearing half shell, which is fixed in the circumferential direction of the switching shaft, by placing the supporting mechanism on the switching pole assembly.